When a jet-powered aircraft lands, the aircraft brakes, various aerodynamic drag sources (e.g., flaps, spoilers, etc.), and, in many instances, aircraft thrust reversers, are used to slow the aircraft down in the desired amount of runway distance. Once the aircraft is sufficiently slowed, and is taxiing from the runway toward its ground destination, the aircraft brakes are used slow the aircraft, and bring it to a stop at its final ground destination.
Presently, many aircraft brake systems include a plurality of hydraulic, pneumatic, or electromechanical actuators, and a plurality of wheel mounted brakes. The brakes in many aircraft are implemented as multi-disk brakes, which include a plurality of stator disks and rotor disks. The stator disks and rotor disks may be alternately splined to a torque tube or wheel rim, and disposed parallel to one another, to form a brake disk packet. The actuators, in response to an appropriate pilot-initiated command, move between an engage position and a disengage position. In the engage position, the actuators each engage the brake disk packet, moving the brake disks into engagement with one another, to thereby generate the desired braking force.
An aircraft brake actuation system, like many other control systems, may exhibit hysteresis. This hysteresis may result from various position control errors and from friction and/or other inefficiencies in various mechanical elements in the system. For example, in an aircraft brake actuation system the actuators may exhibit gear losses, and some compliance may exist between the actuator power unit (e.g., the motor) and the actuator output. Moreover, frictional losses and compliance may exist between the actuator output and the brake disk packet, as well as within the brake disk packet itself. The position control errors can be corrected, or at least made negligible, with appropriate position control schemes. The hysteresis effects due to the various mechanical inefficiency sources are, however, more difficult to address, and can cause errors in control accuracy and a phase shift in system frequency response.
Hence, there is a need for a system and method that compensates for the hysteresis effects that may be exhibited in an aircraft brake actuation system due to one or more sources of mechanical inefficiency. The present invention addresses at least this need.